Sleep is a highly conserved, essential behavior that impacts mental and physical health, but the mechanisms that control sleep are poorly understood. Sleep and sleep homeostasis (increases in sleep after sleep loss) occurs in nearly all animals. In humans, sleep loss impairs learning and memory and is linked to obesity and heart disease. Changes in sleep/wake status are accompanied by changes in the expression of many genes, but what controls these changes is not known. One mechanism that may be important is the regulation of messenger RNAs (mRNAs) by microRNAs (miRs). MiRs are small (22 nucleotide), non-coding RNAs that bind to the 3' un-translated regions of mRNAs and alter their translation and stability. miRs bind to many different mRNA targets, and therefore can regulate the translation of multiple genes at the same time. The abundance of some miRs varies with time of day and amount of sleep, making miRs promising candidate regulators of gene expression during sleep. While a few miRs have been found to affect sleep/wake cycles in Drosophila and mammals, the role of miRs in sleep has not been systematically tested and no miRs required for sleep homeostasis have been identified. The goal of this research is to identify and characterize miRs that regulate sleep and the sleep homeostat. Drosophila will be used to study sleep, because they are a well validated model for mammalian sleep and have powerful genetic tools, including methods for spatial and temporal control of gene expression. In this project, these genetic tools will be used to manipulate expression of genetically encoded inhibitors of miR function called miR sponges. Preliminary studies using this approach have already identified multiple promising miRs, including miR-190. miR-190 expression increases after sleep, and inhibition of miR-190 function impairs sleep and sleep recovery after sleep deprivation. This project aims to (1) identify novel miRs that regulate sleep behavior and sleep homeostasis; (2) determine where and when those miRs are required by expressing miR sponges in different cell types (including neurons and glia) and at different points in the fly lif cycle; (3) to characterize the role of miR-190 in sleep and by identifying its mRNA targets, which are likely to be essential genes for sleep and sleep homeostasis.